1. Field of the Invention
The present disclosure relates to a shielding structure; in particular, to a shielding structure for integrated inductors/transformers.
2. Description of Related Art
Generally, integrated inductors or transformers are configured on a silicon substrate, so when the entire integrated circuit is working the silicon substrate may be coupled with a generated electromagnetic energy, which causes substrate losses and makes the Q factor (the Quality factor, which is the ratio of the power storage and the power consumption) drop. Under two ideal circumstances, substrate losses can almost be prevented. In one, the silicon substrate has an infinitely great resistance, and in the other, the silicon substrate has barely resistance. However, the resistance of the silicon substrate is commonly 10˜15 Ohm-Cm. In this case, when the inductor or the transformer is working at a high frequency, there will be a coupling current generated causing substrate losses when the current flows through the silicon substrate.
Currently, the lower metal layer or the poly-silicon is used to form a shielding structure for integrated inductors or transformers to prevent the silicon substrate from being coupled with the electromagnetic energy. However, the solid shielding structure may cause a large Eddy current effect. In this case, a reverse magnetic field is generated when the current is flowing through the shielding structure and thus the integrated inductors or transformers may be damaged.